Recoil starters for internal combustion engines, such as of the smaller sizes as commonly used on lawn mowers, snow blowers, generators, outboard motors, and the like, commonly employ a pulley defining a groove in which the starter rope is coiled. Upon tensioning of the starter rope the pulley is rotated and connected to the engine to crank and start the engine. Recoiling of the rope upon the starter rope pulley is accomplished through a spiral spring connected to the pulley and a stationary anchor whereby the spring is wound during the cranking rotation of the pulley, and the resiliency of the spring rotates the pulley in the opposite direction to retract the starter rope and rewind the rope upon the pulley groove.
As the technology of recoil starters has developed it is now common practice to shape the pulley rope receiving groove of a particular configuration to facilitate rope re-winding and reduce the force required during pulley rotation while cranking, and it is now common to form the starter rope pulley of synthetic plastic as formed by injection molding processes. Examples of engine recoil starters using spiral springs for recoil purposes, and employing synthetic plastic pulleys, are shown in the assignee's U.S. Pat. Nos. 3,782,355 and 4,492,190.
As the desire for lower profile starters of economical construction has increased recoil starter designers have met the challenges and synthetic plastic starter recoil pulleys are now available wherein the recoil spring is substantially housed within the axial configuration of the rope pulley and the synthetic plastic material forming the pulley also functions as a housing for the recoil spring. However, such construction has created problems in that the very high radial forces existing within the spring as imposed upon the synthetic plastic material of the rope pulley will cause the pulley material to cold flow or "creep" which changes the dimensional conformity of the pulley, and one of the problems that has arisen from such pulley material cold flowing pertains to the retention of the recoil spring anchor upon the pulley.
It is common to form the ends of the spiral recoil spring with a partial loop or hook formed of the spring material. This hook is received within anchor pins, slots or recesses defined on the pulley housing or engine structure, and normally, the resiliency of the spring in a rotative unwinding direction tending to maintain the spring end hooks in engagement with their anchors is sufficient to maintain the desired assembly between the spring and its hooks. However, upon the occurrence of pulley dimensional change due to cold flowing of the pulley material it is possible that, over a period of time, the dimensional changes may be of such value as to permit the spring end hook associated with the pulley to disengage from its pulley anchor slot rendering the recoil spring inoperable.
This tendency to disengage the recoil spring hook from its associated pulley anchor slot is also aggravated by the inertial dynamics occurring during pulley reversals in that during the sudden stopping and starting of the pulley rotation the inertial rotative movements of the spring and pulley will tend to disengage the spring end hook from its slot.
Previously, solutions to the aforedescribed problems with respect to recoil starter rope pulleys have not been successfully overcome.
It is an object of the invention to provide a rope pulley construction for engine recoil starters wherein the recoil spring includes a hook associated with a slot anchor defined in the pulley and a spring end lock is defined on the pulley for maintaining the engagement between the spring end and the pulley under dimensional pulley stress or inertial dynamics.
Another object of the invention is to provide a rope pulley construction of synthetic plastic material wherein the configuration of the pulley includes a recess for receiving the spiral recoil spring and the anchor between the pulley and outer spring end is of such configuration to maintain the spring-pulley anchor connection even under dimensional changes of the pulley due to cold flow of the pulley material.
In the practice of the invention a rope pulley for an engine recoil starter includes a hub whereby the pulley may be concentrically rotatably mounted relative to a rotating engine part, usually the crankshaft. Unidirectional clutch structure, which constitutes no part of the instant invention, is used to connect the pulley hub to the engine during rotation of the rope pulley in an engine cranking direction. During recoil rotation of the rope pulley in the rope retracting direction the pulley is disengaged from the engine structure, and such disengagement also occurs when the engine starts.
The synthetic plastic pulley includes a peripheral region in which a groove is defined by flanges for receiving the starter rope, the rope being coiled within the groove when the rope is retracted by recoiling, and tensioning of the rope rotates the pulley to crank the engine.
The pulley includes a recoil spring receiving recess concentrically related to the pulley axis of rotation, and the spring recess is substantially in radial alignment with the rope receiving groove and is outwardly defined by an axially extending wall against which the outer coils of the spring engage. The outward radial forces of the spring are imposed against this axial pulley wall.
The spring receiving recess axial wall is provided with an elongated axially extending slot which receives the outer hook end of the recoil spring. The spring hook end extends through the slot forming a positive connection between the spring and pulley for imposing a torque force on the pulley during rope recoiling, and as the engine is cranked the pulley imposes a torsional winding force upon the spring.
Spring outer end locking features are defined on the pulley structure which coordinate with the dimensions and form of a spring end hook to maintain proper hook position once assembled. A primary feature of the lock is a radially extending cap plate which is reinforced against axial deflection by a homogeneous web extending between the cap plate and the adjacent pulley flange. The cap plate is superimposed over a portion of the spring hook end received within the pulley slot in an axial direction corresponding to the "open" end of the slot and the spring receiving recess. Accordingly, the cap plate prevents the coil spring end from axial displacement in the direction toward the open end of the anchor slot and the retainer cap plate effectively assures engagement and proper positioning of the recoil spring outer hook end with the pulley slot anchor even though limited axial displacement of the spring in the direction of the open ends of the spring receiving recess and anchor slot may have occurred.
Dynamic movement of the spring end in a direction which will remove the spring end hook from the pulley slot only occurs when the spring is not wound tightly and wherein several spring coils are stacked in contiguous relationship against the pulley recess in which the spring coil is located. In such instance the movement of the outer spring hook will be tangential to the spring receiving pulley recess and in such instance the rear end of the hook will engage the rear of the pulley slot before the free end of the hook moves out from under the cap plate. During assembly, the spring can be wound closely to the axis of the pulley allowing the tangential extension of the outer end of the spring to be a position which passes through the pulley slot at an angle. The configuration of the cap plate and its associated structure is such as to permit ease of assembly of the spring to the pulley and its slot, and yet, under operating conditions the spring end is locked with respect to the pulley slot and is retained against axial displacement.